BERLIN — The Tunisian who drove a truck into a Berlin Christmas market last year may have avoided deportation because German authorities were slow to pass on a handprint demanded by his home country.

Twelve people were killed in Dec. 19 attack later claimed by the Islamic State group. Suspect Anis Amri died in a shootout with Italian police.

The Berliner Morgenpost newspaper and public broadcaster RBB reported Monday that Tunisia demanded the handprint before issuing identity documents for Amri after Germany rejected his asylum in June 2016.

Germany’s Federal Police Office confirmed Tuesday it had held Amri’s handprints since July 2015, but said it only learned in August 2016 that they were required for his expulsion.

The Amri case has exposed numerous mistakes by German authorities in tracking a known extremist .